Mobile power concrete saw device having an adjustable cutting disc



June 2, 1959 H. R. wlLsoN 2,889,141

MOBILE POWER CONCRETE SAW DEVICE HAVING AN ADJUSTABLE CUTTING DISC Filed Oct. 5, 1956 3 Sheets-Sheet 1 i 71540 git? 4RM/1,503 W1 www by @ggf/12 MQW @Rll'orn/g;

H. R. WILSON CONCR June 2, 1959 2,889,141 MOBILE POWER ETE SAW DEVICE HAVING 4 AN ADJUSTABLE CUTTING DISC Filed Oct. 3. 1956 3 Sheets-Sheet 2 III June 2, 1959v R wlLsoN 2,889,141

H.` MOBILE POWER CONCRETE SAW DEVICE HAVING AN ADJUSTABLE CUTTING DISC Filed Oct. 3, 1956 V:s sheets-sheet :s

` ,rwentof uw fI2. @Wi 15011 United States MOBILE POWER CONCRETE SAW DEVICE HAV ING AN ADJUSTABLE CUTTING DISC Harry R. Wilson, Waterloo, Iowa, assgnor to Engineered flquipment Inc., Waterloo, Iowa, a corporation of owa Application October 3, 1956, Serial No. 613,640 5 Claims.` (Cl. 262-20) This invention relates to the art of cutting solidified concrete and more particularly to a device for cutting slits in concrete slabs to replace the common expansion joint.

Highway engineers have adopted a new practice for conditioning their concrete roadways to the stresses imposed upon the concrete-both from the inherent conduct of the material itself and from the loads subjected on the concrete from normal highway use. A slab of concrete will possibly crack even if no loads are ever placed thereon. These cracks may be caused by the surface tension of the drying concrete, or from the effects of extreme temperature which may cause expansion or contraction of the material. Herebefore, asphaltic expansion joints have been employed between various sections of the concrete slab, `and the purpose of these joints was to absorb the stresses within the concrete and prevent or at least control any cracking of the slab. However, the new common practice to combat these stresses in the concrete is to cut a narrow slit of predetermined depth in the concrete at the same general location where expansion joints were formerly placed. This narrow slit serves in one sense as an expansion joint for it releases the tension in the upper fibers of the concrete. Furthermore, any cracks which do appear in the slab develop along the bottom of these slits on the same principle that a glass cutting tool induces shearing weakness to a piece of plate glass. Furthermore, any crack that appears in the bottom of the slit is composed of many interlocking surfaces by virtue of the impossibility of obtaining a straight shearing line through the complex aggregate of the concrete. These interlocking surfaces keep the two sections adjacent the slit from slipping vertically past each other. My device is designed to place these beneficial slits in the concrete.

The slit cutting operation takes place after the green concrete has obtained its original set.

Therefore, the principal object of my invention is to provide a concrete slit cutting device which can have its cutting disc selectively removed from its cutting operation without altering or adjusting the depth control mechanism of the cutting disc.

A further object of my invention is to provide a concrete slit cutting device that will automatically throttle back its power means when the cutting disc is disengaged from its cutting operation.

A still further object of my invention is to provide a concrete slit cutting device whose center of gravity is substantially over the cutting disc, so that the yweight of the unit will assist in keeping the cutting disc in uniform contact with the concrete.

A still further object of my invention is to provide a concrete slit cutting device that has a transmission with an infinite number of speeds so that the speed of the device can be regulated through control of the transmission rather than through the uncertain coordination between transmission and motor speed.

A still further object of my invention is to provide a Patented June 2, 1959 concrete slit cutting device that is durable in use, economical of manufacture, and rened in appearance.

These and other objects will be apparent to those skilled in the art.

My invention consists of the construction, arrangement, and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, specifically pointed out in my claims and illustrated in the accompanying drawings, in which:

Fig. 1 is a perspective view Fig. 2 is `a rear elevation of my device with portions of the various cover members cutaway,

Fig. 3 is a side elevational view of my device taken on line 3-3 of Fig. 2, with the cutting disc in its lowered, cutting position,

Fig. 4 is a plan View of the hand crank on the apparatus by which the depth of the slit in the concrete is regulated,

Fig. 5 is a partial sectional view taken on line 5-5 of Fig. 3, and

Fig. 6 is a partial sectional view of the treadle means of my device in use,

and its locking device, and the dotted lines in this figure show how `the treadle is unlocked.

I have used the numeral 10 to designate an intermediate frame on my device, and this frame is substantially rectangular in shape. Mounted in any convenient manner to frame 10, such as by cradle 11, is the conventional internal combustion motor unit 12. The motor 12 has a conventional throttle on its carburetor, but the details of this throttle, not being a part of my invention, are not shown on the drawings. Bolted or otherwise attached to the lower rear side of frame 10 are L-shaped bearing members 14 and 16. The lower flange of these L-shaped members 14 and 16 extend in a rearward direction, `as shown in Fig. 5. The forward and upper portions of bearing members 14 :and 16 form semi-enclosed housings which are designated by the numerals 17 and 18, respectively. Bolted or otherwise secured to the lower inside walls of housings 17 and 18 are shaft bearing members 19 and 2t), respectively. Shaft bearing members 19 and 20 are clearly shown in Fig. 5. Rotatably journaled in bearing members 19 and 20 is shaft 22. A beam member 24 is rotatably secured at one of its ends by a shaft housing 26 to one end of shaft 22. Beam 24 extends in a forwardly direction and terminates 'in a shaft housing 2d. The longitudinal axis of shaft housing 28 is parallel to the longitudinal axis of shaft 22. Beam member 341, which is very similar to beam 24, is also rotatably secured to shaft 22 by bushing 32 in spaced apart relation from beam 24. Beam 30 extends forwardly and substantially parallel to beam 24 land terminates in a shaft housing 34 whose longitudinal axis coincides with the longitudinal axis of shaft housing 28 on beam 24. Rotatably mounted within housings 28 and 34 is shaft member 36. Collars 37 and 38 are rigidly secured by rivets 35 to the outside ends of housings 28 and 34, respectively. Plates 39, which are perpendicularly disposed to the longitudinal axis of shaft 36, extend upward from collars 37 and 33. The ends of shaft 36 are threaded and extend beyond the outside ends of housing members 28 and 34. Each end of shaft 36 is adapted to receive a conventional washer 40, a lirst bearing disc 41 which isrigidly secured to shaft 36, a second bearing disc 42 which movably embraces shaft 3,6, and a locking nut 43 which can lock the two bearing discs 4l and 4Z together. Any circular cutting disc 44 can thereby be locked between the bearing discs by re-` moving the nut 43 and disc 42 from the shaft 36, placing the cutting disc on the shaft tightening disc 42 and `nut 43 44 and bearing disc 41.

against the cutting disc Detachably secured to plate 39 in any convenient rnan-` zand then replacing and" ner, such as by bolts 45, is housing 46. Housing 46 is adapted to nt over cutting disc 44 and is clearly shown in Fig. 3. This housing has a circular cut away portion in each side with bolt holes 47 so that the housing can be used on plate 39 at either end of shaft 36. The interchangeability of housing 46 is aptly illustrated by the dotted lines in Fig. 5. The forward portion 48 of housing 46 is connected to the main part of the housing by hinge 51. This arrangement provides easy yaccess to the cutting disc 44 for inspection purposes. A flexible shield 49 is riveted to the trailing edge of housing 46 to control the fright of concrete particles from the cutting disc 44.

By again observing Pig. 5, it can be seen that a pulley drum 50 is rigidly connected to shaft 22 between beam members 24 and 30. A similar pulley drum 52 is rigidly secured to shaft 36 at a point which is also between beam members 24 and 30. A plurality of continuous belts 54 extend between pulley drums 50 and 52 so that rotation of drum 50 will induce rotation to drum 52.

Rigidly connected to the inside face of the lower, rearwardly extending anges of bearing members 14 and 16 are shaft bearing members 55. Rotatably extending through bearing members and the anges of members 14 and 16 is shaft 56. Rigidly connected to the ends of shaft 56 are drive wheels 58 which provide the propelling force for the unit. A pulley drum 60 is rigidly secured to shaft 56 and is operatively connected to a transmission means which will be discussed hereinafter.

A mounting member 62 is rigidly connected in any convenient manner to the rear of frame 10. Member 62 has a rearwardly extending arm 63 at its top, and. arm 63 has two shaft bearing members 64 which rotatably support shaft 66. By referring to Fig. 2, it can be seen that a drive wheel 68 is rigidly secured to the outer end of shaft 66, and frictional wheel 70 is rigidly secured to the other end of shaft 66. Gear box 72 is rigidly secured to the rear side of mounting member 62. The longitudinal axis of the vertical shaft 74 and horizontal shaft 76, which extend from gear box 72, are in a substantial vertical plane below shaft 66. A pulley drum '78 is rigidly secured to the outer end of shaft 76 and is aligned with the pulley drum 60 on shaft 56. Belts S0 loosely engage drums 78 and 66. A conventional belt tightening device to selectively tighten belts titi on drums '78 and 60 is comprised of hand lever 81, linkage 82, shaft 83, arm 84, and roller-shaft 85.

A frictional wheel 86 is rigidly secured to the vertical shaft 74. Wheel 86 is very similar to the frictional wheel 70 on shaft 66. Interposed between wheels 86 and 70 is my transmission unit which can be seen in Figs 2 and 3. Wheels 86 and 70 have beveled, radial frictional surfaces which are adapted to rotatably engage the outer surface of the hollow dome member 88, which has the shape of half a geometric sphere. A shaft passes through the geometric center of the spherical dome 88 and extends up to the geometric center of the inside surface of the dome, where it is rigidly attached. Shaft 90 is rotatably journaled in bearing member 92. Not shown in Fig. 3 is a small lug on shaft 90 which prevents shaft 90 from sliding or moving through bearing member 92. Bearing member 92 is rotatably mounted between frame members 93 and 94, which in turn are mounted on arm 95. Arm 95 is rigidly connected to support arm 96, which in turn is pivotally connected to mounting member 62. A linkage member 97 is rigidly secured to and extends perpendicularly from arm 96. A rod 98 extends through the end of member 97 and also extends upward through a clip angle 99 that is rigidly secured to mounting member 62. Nuts 100 are on each end of rod 98. A spring 101 is compressed between clip angle 99 and the nut 100 on the upper end of rod 98. The compressed spring 101 tends to rotate arm 96 upward, as seen in Fig. 2, which, by virtue of the above described 4 parts, tends to keep dome member 8S in pressured contact with frictional Wheels 70 and 86.

A worm gear 102 is rigidly connected to the end of crank shaft 103, which in turn is rotatably supported in any convenient manner such as by the U-shaped shaft bearing member 104. Worm gear 102 is adapted to mesh with gear 106 which is rigidly connected to the end of bearing member 92. Gear 106 and bearing member 92 have the same axis of rotation. Thus it can be seen that the turning of handle 108 on the outside of crank shaft 103 will result in the rotation of gear 106 and bearing member 92, which in turn will rotate shaft 90 and dome member 88 in a vertical plane about the axis of rotation of bearing member 92. It is obvious that the vertical rotation of dome member 88 about this axis will place frictional wheels 86 and 7i) at varying distances from the geometric center of the outside surface of the dome. This vertical rotation of dome 88 will always bring one of the frictional wheels 86 and 70 nearer the geometric center of its surface, and will always bring the other lwheel to a point further away from this geometric center. Obviously, the wheel nearer that center will move at a slower rate of speed than the wheels further away from the center when the dome member 88 is induced to spin about the axis defined by shaft 90. It should be noted that if the frictional engagement between worm gear 102 and gear wheel 106 is not sufficient to prevent rotation in a vertical plane of dome 88 while the unit is in operation, any convenient means can be utilized to selectively hold shaft 103 and handle 108 against rotation, which would operatively selectively lock dome 88 against vertical rotation from its predetermined position.

Motor 12 has a conventional drive shaft 110 on which is rigidly mounted a pulley drum 112. Belts 114 extend downwardly from pulley drum 112 to pulley drum 116 which is rigidly secured to shaft 22. Belt 118 extends from pulley drum 112 to drive wheel 68. Thus the propelling power of my device can be traced from the motor drive shaft through belt 118 and wheel 68 to shaft 66, thence through the above described transmission means; thence to Wheel 86 and shaft 74, gear box 72 and shaft 76, and thence to drive shaft 56 by belts 80. The power from the motor is transmitted to the cutting disc from the motor drive shaft 110 to shaft 22 by belts 114, and then to shaft 36 from shaft 22 by belts 54.

Two triangular frame members 120 and 121 are rigidly secured to frame 10 and extend rearwardly therefrom. Frame members 120 and 121 are connected at their tops by brace 122 and the resulting frame is detachably covered by housing 124, as shown in Fig. l. Tube members 126 and 127 are rigidly secured to the tops of frame members 120 and 121, respectively, and these tube members extend in a substantial rearward, parallel, horizontal direction. Sleeves 128 are rigidly secured to the rear ends of tubes 126 and 127, and these sleeves 128 are each equipped with a set screw 129 which is in adjustable contact with the interior of the sleeve. Handle portions 130 are telescopically inserted into tubes 126 and 127 and are made length adjustable by the obvious use of sleeves 128 and set screws 129.

Vertical pipe 132 is rigidly secured to brace member 122. Rotatably and slidably mounted within pipe 132 is rod 134, which extends out of the lower end of pipe 132 and terminates in a bar 135. The upper end of rod 134 has a threaded, hollow portion adapted to receive threaded rod 136. Rod 136 extends through a hole in the top of brace 122, and terminates in a cap 137 which prevents the downward movement of rods 134 and 136 into pipe 132. A crank member 138 comprised of an elongated portion 139 and a handle portion 140 is pivotally connected to cap 137 by downwardly extending ear portions 141 `which are disposed on one end of the elongated portion 139. A pin 142 creates the pivotal connection between the crank 138 and cap 137 by exaesafil tending through the cap 137 and ears 141. A downwardly extending tongue 143 is disposed on the end of crank 138 lforward of the ear portions 141. Tongue 143 is adapted to penetrate any one of a plurality of holes 144 in the top of brace 122 around cap 137. This structure is clearly shown in Fig. 4. A spring 146 is secured to the top of cap 137 and tends to hold crank 138 in an inclined position as shown in Fig. 3, by exerting an upward pressure on the bottom of elongated portion 139. The purpose of spring 146 is to selectively keep tongue 143 in one of the holes 144 so as to prevent any inadvertent rotation of cap 137 and rod 136 with respect t0 rod 134. It is obvious that the crank can be freely rotated by compressing spring 146 and thus removing the tongue 143 from any of the holes 144.

Referring now to Figs. 3, and 6, it can be seen that there is a plurality of holes 147, 148 and 149 in the bar 135 on rod 134. Slidably embracing bar 135 is a pin sleeve 150 whose bore extends in a horizontal rearward direction. Lugs 151 are placed above and below the extreme position of holes 148 and 149 on bars 135 to limit the sliding displacement of sleeve 15|) upon bar 135. Slidably mounted Within the sleeve 150 is pin 152 which extends from the rearward end of the bore and is pivotally connected to the end of linkage member 154 by pin 155. The other end of linkage member 154 is pivotally connected by pin 156 to a downwardly extending arm 158 on treadle 160. A beam member 162 is pivoted at its rear end to arm 158 by pin 163. Sleeve 150 is pivoted to the beam 162 by means of a bearing pin 153. Beam 162 extends forwardly from treadle 160 and lies in the same vertical plane as pin sleeve 150, linkage member 154 and bar 135. As shown in Fig. 5, beam 162 has an opening 164 which loosely encloses the bar 135. The forward end of beam 162 is depressed at a slight angle to facilitate its rigid attachment to beam 24 by bolts 165 at a point on beam 24 just forward of shaft 22.

A spring member 166 extends over the top of the rear end of beam 162, then ground pin 163 and terminates on the underneath side of treadle `160. The effect of spring 166 is to force treadle 160 to rotate in a counter-clockwise direction, as shown in Fig. 3, which will always force pin 152 forward into pin sleeve 150 and any of the holes 147, 148 or 149 on bar 135 which might be aligned with the core in the pin sleeve 150; With the pin inserted and held within one of the holes 147, 14S or 149, as shown in Fig. 5, the pin sleeve 150 cannot slide vertically upon the bar 135. And since the sleeve 150 is operatively connected to beam 162, the locking of sleeve 150 results also in the locking of beam 162 against any vertical movement. Consequently, the cutting disc 44, which is operatively connected to beam 162 by beam 24, is also fixed against vertical movement. Pin 152 may be withdrawn from its locking engagement with holes 147, 148 or 149 by rotating treadle 160 clockwise as shown by the dotted lines in Fig. 6. Then sleeve 150 is free to slide vertically on portion 135, which in turn will permit vertical movement of both beam 162 and cutting disc 44. It should be noted that the unit comprising beam 162, beam 24 and cutting disc 44 rotates upon shaft 22 whenever movement is imposed upon that unit. It should be further noted that beam 24 is of greater length and mass than beam 162 so that if the above unit is uninhibited by the action of pin 150 and treadle 160, the cutting disc will automatically move downwardly. The downward position of the above unit is shown by solid lines in Fig. 3. Assuming that the unit is locked in that position by pin 156, as described herebefore, the operator can raise the cutting disc to the position shown by the dotted lines in Fig. 3, by disengaging pin 150 through the slight forward rotation of treadle 160. Then, by exerting a downward force upon treadle 160, the unit can be rotated about shaft 22 to raise the cutting disc to 6.. its elevated position. by the insertion of pin 152 in the hole 149.

It is obvious at this point that the location of the holes in the bar on the lower end of rod 134 is a very critical one, for the location ot these holes determines the elevation of the cutting disc when the cut-V ting disc is in its locked, operating position. I'he height of the top hole 148 will determine the elevation of the cutting disc when the slit is being cut in the concrete. Obviously, the height of this uppermost hole 148 can be predetermined by adjusting the height of rod 134 within pipe 132 by screwing rod 136 into or out of -rod 134 with crank means 138. The height of this uppermost hole 148 Will control the depth of the slit to be cut. The bottom hole 149 in bar 135 is merely used to lock the cutting disc in its upward position when the slit cutting operation is not taking place. An intermediate hole 147 can be employed at the convenience of the operator as either a cutting or non-cutting position for the disc 44, depending upon what elevation this intermediate hole happens to have been placed. The important thing to be noted is that once the cutting depth of the disc 44 has been determined by the elevation of the top hole 148 in rod 134, the cutting disc 44 can be lowered and `raised without any adjustment in this cutting depth by the locking and unlocking of pin and the subsequent rotation of beam members 162 and 24 upon shaft 22.

A clip angle 167 is rigidly secured to the top of beam 162 and a pulley Wheel 168 is rotatably secured thereto. This structure is clearly shown in Fig. 3. A linkage member is pivoted in any convenient manner to the outside of pipe 132 and a second linkage member 171 is similarly pivoted to rod 134 and the approximate midpoint of member 170. A cable 172 is secured to the end of member 170, threaded about pulley wheel 168 and` operatively connected by pulley wheels 169 to the throttle lever on engine 12. The throttle lever is moved to its opened position, beam 162 is moved to its elevated position, and then cable 172 is drawn substantially tight and secured. Then when beam 162 is lowered lto remove the cutting disc from its cutting operation, pressure is exerted uponcable 172 by the downward moving beam 162 to close the throttle down While the cutting disc is in its inoperative position. The usual spring actuated throttle lever on motor 12 will automatically open when the pressure on cable 172 is relieved by the cutting disc as it once again resumes its cutting position as beam 162 moves upward. It is sometimes necessary to reverse the conventional spring on the throttle lever of a motor so that the spring urges the opening of the throttle rather than the closing of the throttle. The above described throttle control is adapted! -to control a throttle lever whose conventional spring yieldingly holds the throttle open. It can be seen from the above that the engine 12 will automatically be throttled back when the cutting operation ceases, and automatically throttled forward when the cutting operation commences. This is accomplished without manual assistance.

Leg members 174 are rigidly secured to the forward part of frame 10. Rotatably secured to leg members 174 are wheels 176. These independently turning wheels 176 are not secured to any source of power, and when the cutting disc has been removed from its slit and the operator wishes to turn the whole device before moving to a new location, he needs only to exert a slight lifting force on the handles 130, and the entire Weight of the unit is thereupon supported by wheels 176. This act is facilitated by the fact that the heavy motor 12 is substantially above wheels 176, thereby relieving the operator from lifting much weight by the handles. The motor 12, which represents the bulk of the weight of the total unit, has obviously been placed substantially for- Wardso that its weight would assist in keeping the cut- It can be locked in this position ting disc 44 on the forward part of the machine in continuous cutting engagement with the concrete during the cutting operation.

A guide marker 177 is secured to the outside of leg member 174 and is aligned with cutting disc 4,4. A guide frame173 is rotatably suspended from the front of frame 10. Guide frame 178 is comprised of forwardly extending arms 179 which are connected at their outer ends by hollow tube 130. Guide marker 131 is capable of telescopically entering either end of tube 180 and the outer blade 182 on marker 131 is aligned with cutting disc 44 and guide marker 177. Set screw 183 detachably retains marker 181 in tube 180. A line 134 is scribed on the concrete in the path where theslit is to be cut. Markers 131 and 177 are aligned with the cutting disc to assist the operator in following the line 184 while cutting the slit. A rope 185 makes the guide frame height adjustable by selectively securing-it to any portion of the frame 1t) or motor 12, after rst securing it to brace 136 on guide frame 178.

The normal operation of my device is as follows: The cutting disc 44 and guide markers 177 and 181 are aligned over line 184. The motor 12 is started but belts 80, which connect the transmission to the drive shaft 56 and drive wheels 58, are left in their untightened condition so that the unit will not move. The cutting disc is locked in its elevated position shown by the dotted lines of Fig. 3. The operator then disengages pin 152 from hole 1491 in the lower end of bar 135 by rotating treadle 160 slightly forward. Since beam 24 is of greater length and mass than beam 162 cutting disc 44 will move towards the ground'without effort by the operator. As cutting disc 44 moves downwards towards its cutting position, the pressure is reduced on cable 172 and the spring on the throttle of motor 12 automatically opens, thus giving the cutting disc additional speed and power. The cutting disc isthen permitted to cut downward to any desired predetermined depth, and when this depth has been reached, rod 134 is screwed downward by crank 138 and rod 136V so that the uppermost hole 14S on bar 135 coincides with pin 152 in sleeve 151?. Pin 152 can then enter this hole 148 and the cutting disc is then locked in its cutting position. This is just one of several apparent ways that the hole 143 could be aligned with pin 152 so as to arrive at a slit of proper depth.

The handle 81 on the belt tightening apparatus for belts 80 isfthen moved downward in conventional fashion to tighten the belts and connect drive wheels SS with the transmission. Handle 108 on shaft 1113 can be turned until the desired ratio of speeds is created by dome Sd between friction wheels 70 and 86.

Thus, the depth of cut and speed of the machine are determined. After a given slit has been cut and it is desired to move the machine to another location, the operator disengages pin 152 from hole 143 by rotating the treadle 160 slightly forward, and then he pushes the treadle downward and locks pin 152 in a hole 149 of bar 135 by allowing spring 166 to rotate treadle 1e() to the rear. This action will raise the cutting disc from the slit and lock it in an elevated position. The downward movement of beam 162 during this operation will pull cable 172 downward and automatically throttle down the motor. If it is desired to turn the machine, the operator needs only to lift upward on the handles 130 to suspend the whole unit on independently turning wheels 176. The unit can then easily be turned without interference from the drive wheels 53 or cutting disc 44. Since the motor 12 has been placed substantially over the cutting disc 445 to keep the disc in continuous Contact with the concrete during the cutting operation, and since the wheels 176 are also substantially directly underneath engine 12, the operator has very little weight to lift during the turning operation.

From the above, it can be seen that the cutting disc can be selectively removed from its cutting operation without adjusting the depth control mechanism. It can also be seen that the throttle of the engine is automatically coordinated with the cutting disc to supply power when it is needed and to reduce power when it is not needed. It will also be observed that since the center of gravity of the machine is substantially over the cutting disc, the cutting disc will be held in continuous contact with the concrete during the cutting operation. It will also be observed that the machine is equipped with a transmission which can propel the unit at an infinite number of speeds without any adjustment of the throttle means. lt is therefore obvious that the above described invention completely attains all of its stated objectives.

Some changes may be made in the construction and arrangement of my mobile power concrete saw device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modiiied forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim:

1. In a concrete cutting device, a frame, a power unit mounted on said frame, a drive shaft with drive wheels thereon secured to the bottom of said frame, a variable speed transmission unit having an infinite number of speeds operatively connected to said power unit, a beam operatively pivotally connected to the bottom of said frame, a concrete cutting disc rotatably secured to the forward end of said beam and operatively connected to said power unit, a vertical pipe rigidly secured to the rear of said frame, a rod slidably mounted in said pipe, said rod having its lower portion extending from the bottom of said pipe, said lower portion of said rod having a plurality of holes therein, a sleeve having a bore slidably mounted on said lower portion of said rod, a pin slidably mounted in the bore of said sleeve and adapted to enter said holes in said lower portion of said rod whenever the bore of said sleeve is adjacent one of said holes, a treadle pivoted to the rear end of said beam and operatively pivotally connected to said pin, a spring means connected to said beam and said treadle to operatively yieldingly urge said pin into said sleeve, and means connected to said rod for adjusting its elevation with respect to said pipe.

2. In a concrete cutting device, a frame, a power unit having a throttle mounted on said frame, a drive shaft with drive wheels thereon secured to the bottom of said frame, a variable speed transmission unit having an infinite number of speeds operatively connecting said power unit and said drive shaft, a beam operatively pivotally connected to the bottom of said frame, a concrete cutting disc rotatably secured to the forward end of said beam and operatively connected to said power unit, a vertical pipe rigidly secured to the rear of said frame, a rod slidably mounted in said pipe, said rod having its lower portion extending from the bottom of said pipe, said lower portion of said rod having a plurality of holes therein, a sleeve having a bore slidably mounted on said lower portion of said rod, a pin slidably mounted in the bore of said sleeve and adapted to enter said holes in said lower portion of said rod whenever the bore of said sleeve is adjacent one of said holes, a treadle pivoted to the rear end of said beam and operatively pivotally connected to said pin, a spring means connected to said beam and said treadle to operatively yieldingly urge said pin into said sleeve, means connected to said rod for adjusting its elevation with respect to said pipe, and a means operatively connected to said beam and said throttle so that said throttle will open when said cutting disc is lowered, and said throttle will close when said cutting disc is raised.

3. In a concrete cutting device, a frame, a power unit mounted on said frame, a drive shaft with drive wheels thereon secured to the bottom of said frame, a dome member having the shape of a half sphere operatively rotatably secured to said frame and capable of pivoting in a vertical plane with respect to said frame, a first frictional wheel operatively connected to said power unit and rotatably engaging the outside surface of said dome, a second frictional wheel operatively connected to said drive shaft and rotatably engaging the outside surface of said dome, the axis of rotation of said first and second frictional wheels being perpendicular to each other, a means on said dome for adjusting its pivotal angle with said frame, a beam operatively pivotally connected to the bottom of said frame, a concrete cutting disc rotatably secured to the forward end of said beam and operatively connected to said power unit, a -vertical pipe rigidly secured to the rear of said frame, a rod slidably mounted in said pipe, said rod having its lower portion extending from the bottom of said pipe, said lower portion of said rod having a plurality of holes therein, a sleeve having a bore slidably mounted on said lower portion of Said rod, a pin slidably mounted in the bore of said sleeve and adapted to enter said holes in said lower portion of said rod whenever the bore of said sleeve is adjacent one of said holes, a treadle pivoted to the rear end of said beam and operatively pivotally connected to said pin, a spring means connected to said beam and said treadle to operatively yieldingly urge said pin into said sleeve, and means connected to said rod for adjusting its elevation with respect to said pipe.

4. In a concrete cutting device, a frame, a power unit having a throttle mounted on said frame, a drive shaft with drive wheels thereon secured to the bottom of said frame, a variable speed transmission unit on said frame having an innite number of speeds, said transmission unit operatively connecting said power unit and said drive shaft, a beam operatively pivotally connected to the bottom of said frame, a concrete cutting disc rotatably secured to the forward end of said beam and operatively connected to said power unit, a first means connected to said frame and the rear end of said beam to limit the pivotal angle of said beam with respect to said frame and to permit selective locking of said 'beam within its pivotal Iangle, a second means connected to said rst means for selectively adjusting the elevational limits of the pivotal angle of said beam, and a means operatively connected to said beam and said throttle so that said throttle will open when said cutting disc is lowered, and said throttle will close when said cutting disc is raised.

5. In a concrete cutting device, a frame, a power unit having a throttle mounted on said frame, a drive shaft with drive wheels thereon secured to the bottom of said frame, a variable speed transmission unit on said frame having an infinite number of speeds, said transmission unit operatively connecting said power unit and said drive shaft, a beam operatively pivotally connected to the bottom of said frame, a concrete cutting disc rotatably secured to the forward end of said beam and operatively connected to said power unit, a first means connected to said frame and the rear end of said beam to limit the pivotal angle of said beam with respect to said frame and to permit selective locking of said beam within its pivotal angle, and a second means connected to said rst means for selectively adjusting the elevational limits of the pivotal angle of said beam.

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